Nerve agents, poison and window falls. Over the years, Kremlin foes have been attacked or killed

The attacks range from the exotic — poisoned by drinking polonium-laced tea or touching a deadly nerve agent — to the more mundane of getting shot at close range. Some take a fatal plunge from an open window.

Over the years, Kremlin political critics, turncoat spies and investigative journalists have been killed or assaulted in a variety of ways.

None, however, has been known to perish in an air accident. But on Wednesday, a private plane carrying a mercenary chief who staged a brief rebellion in Russia plummeted into a field from tens of thousands of feet after breaking apart.

Assassination attempts against foes of President Vladimir Putin have been common during his nearly quarter century in power. Those close to the victims and the few survivors have blamed Russian authorities, but the Kremlin has routinely denied any involvement.

There also have been reports of prominent Russian executives dying under mysterious circumstances, including falling from windows, although whether they were deliberate killings or suicides is sometimes difficult to determine.

Read more: ABC News